1. Field of the Invention
The present invention relates to the technical field of LED test and, more particularly, to a light emitting diode (LED) device with built-in fast self-test circuit.
2. Description of Related Art
In 1995, Rubin Braunstein in the Radio Corporation of America (RCA) first found the infrared radiation from GaAs and other semiconductor alloys. Subsequently, Nick Holonyak Jr. developed the first light emitting diode (LED) for visible light applications in practice.
With the advance of LED technology, the illuminance or usage lifetime of an LED has relatively improved and thus increasingly replaced conventional lights. A cold cathode fluorescent lamp (CCFL) backlight is replaced with an LED backlight, which leads to a simple and concise circuit design and has a higher external force sustainability. Thus, it is more environmentally friendly and vividly displayed as the CCFL backlight of a liquid crystal display (LCD) is replaced with the LED backlight. In addition, when the LED lights replace white lamps, halogen lamps, and the like, it saves more power, becomes brighter, gains longer life, and lights quicker. When the LEDs are used in the brake light of a car, the accident frequency caused by backing a car is reduced. In addition to lighting, most electronic products, such as a motherboard, display card, and network card, use LEDs as indicative lights to indicate the working states of circuit boards.
FIG. 1 is a schematic diagram of a conventional LED test. In FIG. 1, there are a red LED, a blue LED, and a green LED in an LED package 100. A test machine (not shown) controls switches 101, 102, 103 respectively. When the switch 101 is closed, one end of the red LED is grounded and the other end is connected to a high voltage Vdd, thereby lighting the red LED. A spectrometer (not shown) is used to detect the three LEDs by checking whether their saturation is met with the requirement on spectrum.
FIG. 2 is a schematic diagram of a prior LED package 200. In FIG. 2, the LED package 200 has a control and driving circuit 210 to drive respective red, blue and green LEDs based on the data input by the serial input terminal DI. For testing the LED package 200 of FIG. 2, an additional circuit board 220 is required as the prior test machine only provides two signals V+ (with respect to Vdd) and V− (with respect to Gnd). A microprocessor 221 on the circuit board 220 makes use of a serial peripheral interface bus (SPI) to pass one or more test patterns through the DI pin to the control and driving circuit 210.
FIG. 3 is a schematic view of a DIP4 (dual in package 4) package of FIG. 2. FIG. 4 is a schematic view of an SMT6 (surface mount technology 6) package of FIG. 2. Current LED test machines cannot use the input pin DI to control and drive the red, blue and green LEDs in either the DIP4 package or the SMT6 package to thereby ensure the quality. Thus, the external microprocessor 221 is used in a test, but for a large number of LEDs, the testing speed is too slow. Namely, the LED devices in the DIP4 package of FIG. 3 and the SMT6 package of FIG. 4 are tested in semi-automatic manner, which has the disadvantage of very slow testing speed, resulting in relatively slow production.
Therefore, it is desirable to provide an improved LED device to mitigate and/or obviate the aforementioned problems.